Namiko Watanabe (渡辺 菜三子, Watanabe Namiko) is a character from the original oneshot who dates Ichirō until being blackmailed by Shiga into dumping him. Once the issue is resolved that Ichirō accepts Nanako's death, they visit her sister's grave together as a final goodbye.

Backstory

She had a twin sister named Nanako who died in an accident before graduating middle school, and she is forced to pretend to be her because Ichirō can't accept Nanako's death.